Evidence for O-15 + alpha resonance structures in Ne-19 via direct measurement

States in the astrophysically important Ne-19 nucleus have been populated directly using the O-15(alpha, alpha) O-15 reaction with a radioactive O-15 beam. Due to the challenges involved, this represents the first such O-15 measurement with high resolution and the first dedicated to exploring the cluster structure. This measurement comprises three experiments: the first to develop the O-15 radioactive beam, the second the resonant scattering study, and the third to measure the precise energy loss of O ions in He-4 to reduce systematic uncertainties. The results show evidence for O-15 + alpha cluster structure which could explain earlier results pointing to the increased alpha branching ratio in the astrophysical reaction rate for high-spin near-threshold resonances. Absolute differential cross sections have been measured. Additionally, spins, parities, and partial decay widths, essential for nuclear reaction-rate calculations, have been extracted using an R-matrix analysis.